Project

Biotic recovery; Early Triassic; Ammonoid; Conodont; Spores and Pollens; Carbon Cycle; Global changes; Radiolaria; CO2; Evolutionary rates; Early-Triassic; ammonoids; conodonts; palynomorphs; carbon isotopes; climate

Lead
Lay summary
Reconstructing patterns of recovery in space and time after major mass extinctions is of paramount importance to understand how evolution and species diversification react to large-scale global factors (pCO2, climate, oceanic productivity, sea-level changes, etc.). The study of non-actualistic time intervals of the Earth-Life system is highly relevant for evaluating the biotic and abiotic consequences of the present unabated rate of anthropogenic global changes.Although simple theoretical ecological models based on the growth of a population under stable conditions (e.g. the logistic model) provide some conceptual basis, environmental changes during the recovery phases cannot be put aside since they evidently played a major role. Not only the intensity and but also the frequency of global environmental disturbances may lead to different responses in terms of biodiversity. In particular, whether environmental perturbations closely spaced in time (i.e. the end-Smithian event in the wake of the end-Permian event) delayed or accelerated the biotic recovery remains a challenging issue of great significance for the responses of the Earth-Life system to present day global changes.Beyond the well-known size reduction of organisms exposed to severe ecological stress, patterns of morphological responses such as extreme simplifications (up to the temporary loss of minerlized tissues) have been recently documented among both living and fossil marine organisms. The Early Triassic recovery of a "boom and bust" clade such as ammonoids indicates that intrinsic evolutionary rates can also be dramatically altered as a consequence of extreme stress episodes. Such a "good genes and good luck" answer provides an additional evolutionary mechanism to the traditional ecological view heralded by the incumbency model, which is usually invoked for evolutionary radiations that immediately follow mass extinctions. Ceratitina evidently benefited from both good genes and good luck when facing end-Permian and Early Triassic stresses, as opposed to Ammonitina which probably had equally good genes but lacked any good luck at the close of the Cretaceous.

Direct link to Lay Summary

Last update: 21.02.2013

Number	Title	Start	Funding scheme

Reconstructing patterns of recovery in space and time after major mass extinctions is of paramount importance to understand how evolution and species diversification react to large-scale global factors (pCO2, SO2, climate, productivity in the ocean and on land, sea-level changes, etc.). The study of non-Lyellian time intervals of the Earth-Life system is highly relevant for evaluating the biotic and abiotic consequences of the present anthropogenic global changes.This project concentrates on the Early Triassic biotic recovery, which followed the largest know mass extinction of Phanerozoic. It addresses diversity in time and space of ammonoids and conodonts, two major clades characterized by very high evolutionary rates that allow tracing the short term ups and downs in environmental conditions during the Early Triassic. Radiolaria are here newly added to our portfolio. This clade is known to have been deeply affected by the end-Permian mass extinction, but its recovery pattern is very poorly known. It should bring valuable insights at the level of the zooplankton component, which is a key-player within trophic webs. Radiolaria should also allow constructing correlations between the deep-ocean and the shelves, with the aim of broadening the range of environments under investigation.Reconstructing paleoclimatic fluctuations will be continued by means of palynological studies across a broad range of paleolatitudes. The carbon cycle will be further investigated, with emphasis on organic carbon. Special attention will be devoted to our recent discovery of well-dated Early Triassic coals and their relations with the massive perturbations of the carbon cycle, as well as for the differentiation of the biotic recovery between ocean and land. A new integrative CO2-driven model of recovery will be tested. Beyond the well-known size reduction of organisms exposed to severe ecological stress, patterns of morphological responses such as extreme simplifications (up to the temporary loss of hard tissues) have been recently documented among both living and fossil marine organisms. The Early Triassic recovery of a “boom and bust” clade such as ammonoids indicates that intrinsic evolutionary rates can also be dramatically altered as a consequence of extreme stress episodes closely spaced in time. Such “good genes and good luck” answers provide an additional evolutionary mechanism to the traditional ecological view heralded by the incumbency model, which is usually invoked for evolutionary radiations that ensue from mass extinctions.Technically, this proposal corresponds the fourth year of our ongoing project.